Making better contact lenses

Around the world, more and more people are becoming nearsighted. Today’s younger generations have a much higher incidence of myopia than their parents do, according to public health data, and the rate is expected to keep rising in the years ahead. This creeping loss of distance vision is more advanced in developed countries, where young people spend large amounts of their time indoors. The problem is worst in Asia, where nearsightedness affects roughly half of the population. And it’s much higher in some subgroups.

“In college-age people in South Korea, the rate is over 90%,” says Susan Vitale, a research epidemiologist at the National Eye Institute of the National Institutes of Health. “They’ve got something you could almost call an epidemic on their hands.”

Vitale and coauthors published an analysis that found for people aged 12 to 54 in the U.S., myopia appeared to increase from an average of 25% in the early 1970s to almost 42% in the early 2000s (Arch. Ophthalmol. 2009, DOI: 10.1001/archophthalmol.2009.303).

The good news is that myopia can be corrected with contact lenses, eyeglasses, or vision surgery. Younger people, who are more likely to be nearsighted, prefer contact lenses over glasses. A growing population of young, nearsighted customers will turn to the contact lens industry for innovative products that fit their lifestyles.

In the U.S., about 41 million people wear contacts. The majority of those lenses are soft contacts made of hydrogels, first introduced by Bausch + Lomb in 1971. In addition to myopia, they are also used to correct hyperopia, or poor near vision, and presbyopia, the loss of our eyes’ ability to focus as we age, among other things. But after four decades of improvements, the lenses still fall short of perfection for many users.

Between 30 and 50% of wearers find their lenses so uncomfortable that they return to their eye doctor for help. Up to 20% of wearers stop using them altogether. And eye doctors continue to report adverse effects from infection and inflammation.

Contact lens companies are responding with material, design, and manufacturing innovations they say are making lenses increasingly comfortable and safe. In the future, contacts could go beyond mere vision correction to treat conditions such as myopia in children. And with advances in electronic materials, lenses could start to monitor and treat health conditions by using the eye as a window into the body.

The materials trade-off game
 

The first soft contact lenses were made of a polymer, called a hydrogel, based on the monomer hydroxyethyl methacrylate, or HEMA. When HEMA is polymerized, it becomes hydrophilic and can absorb several times its weight in water. The resulting gel is soft and compatible with the biology of the eye surface, making for a comfortable lens.

Although these first-generation hydrogel lenses were popular with consumers and are still on the market today, they have one main drawback: They don’t allow enough oxygen to pass through to the cornea. Eye doctors noticed that patients who frequently wore their hydrogel lenses all day developed redness in the white part of the eye.

“Your cornea doesn’t have actual blood vessels; it has to get oxygen by diffusion from the air. When that is lacking, your eye builds up extra vessels in the white part of the eye around the cornea,” explains Steve Diamanti, a materials scientist and senior R&D manager at CooperVision, a contact lens manufacturer. If the oxygen starvation is severe enough, he says, it can lead to swelling and blurry vision—a condition called cornea edema.

Starting in the late 1990s, the industry developed hydrogels that incorporate silicone-containing polymers made from molecules such as 3-[tris (trimethylsiloxy)silyl]propyl methacrylate, or Tris methacrylate. Silicone chemistry had already been used to increase oxygen transfer in rigid lenses. In soft lenses, the addition of silicone permits as much as six times the oxygen to reach the cornea compared with first-generation hydrogel lenses.

But making water-hating silicone polymers compatible with water-loving hydrogels was not straightforward. And the combination brought new comfort challenges. Silicone increased the stiffness of the lenses. It also repelled water, causing the lens to dry out and interrupting the surface layer of tears that provides lubrication when a user blinks.

“They would turn into something like a potato chip and could fly out of your eye,” recalls Jay Künzler, a consultant to contact lens companies.

The silicone also attracted lipids from tears that could foul the lenses, says John Pruitt, head of vision care research at Alcon, a contact lens maker that is part of Novartis. “Our primary challenge was to maintain oxygen transfer but minimize or eliminate the downsides.”

One early solution was to plasma-treat the surface of the silicone hydrogel to form an enhanced surface layer only a few hundred atoms thick. The glassy surface was wettable and lipid resistant, but handling could make it crack, Diamanti says.

So researchers dug deeper into the lens itself and created nanostructures that would keep the health benefit of oxygen permeation but negate the uncomfortable realities of silicone. Alcon designed water-gradient zones within the lens. The surfaces of the lens are engineered with hydrogel channels that trap water to make it slippery and comfortable. The core region of the lens contains more silicone channels to transport oxygen to the cornea.

Scientists at CooperVision, in contrast, wanted high water content and a more uniform structure to create very soft lenses, which some users prefer for comfort. That meant making brand-new molecules. “We molecularly bonded hydrophilic groups to the silicone material,” Diamanti says, adding that the resulting material is “inherently wettable.”

Thanks to these innovations, which first hit the market in 2013, silicone hydrogel lenses now have higher water content—up to 80%—for more comfort, according to Künzler. “The data in large clinical studies I see show user tolerance has gone from around 60% to closer to 80 or 90%,” he says.

Patients of Stephen L. Glasser, a Washington, D.C., optometrist, have benefited from the shift. Glasser says wettability is the main concern now because most people spend many waking hours staring at a computer screen, a practice that makes them blink less frequently. But no lens is pefect for everyone, he stresses.

Instead, eye care professionals help patients find the right lens based on their specific environment, physiology, ailments, and habits. “The new lenses give us more bullets in the gun—more variations we can go to based on the problems a patient is having,” Glasser says.

Competition and investment
 

Contact lenses are the ultimate performance polymer product. The industry starts with small amounts of affordable monomers plus specialty chemicals such as activators and polymer cross-linkers. But as a finished product, a year’s supply of lenses sells for hundreds of dollars.

It’s no wonder, then, that big corporations have snapped up contact lens firms in recent years. Alcon was acquired in 2010 by Novartis, which then merged it with its Ciba Vision business. Bausch + Lomb was bought by Valeant Pharmaceuticals. Johnson & Johnson has long owned the popular Acuvue brand. The other large manufacturers, CooperVision and the Japanese firm Menicon, remain independent.

Overall, the global contact lens industry is worth an estimated $7.2 billion per year and is growing by 5% annually. Sales in the U.S. totaled about $2.5 billion last year, according to Jason J. Nichols, a professor of optometry at the University of Alabama, Birmingham, and editor of the industry journal Contact Lens Spectrum.

The big five manufacturers own about 80% of the market. The other 20% of patients turn to custom manufacturers for rigid lenses or soft contacts in unusual sizes or prescriptions.

The main players have a high amount of brand competition. In 2016, CooperVision spent 37% of its revenue on sales and supporting activities, an amount similar to what other firms in the consumer products industry spend. But compared with most consumer goods companies, lens makers have a bigger footprint in the raw material supply chain.

“We make all our lenses in-house, and we make many of the polymers we use,” Alcon’s Pruitt says. He says the company even makes some of its own silicone monomers or has them custom made, though it also buys bulk monomers from suppliers.

Chemical companies that supply the contact lens industry tend to be small firms that have close, long-term relationships with their customers, says Carrington D. Smith, chief executive officer of MPD Chemicals. MPD is the parent of Monomer-Polymer & Dajac Labs and Silar, sister firms that sell raw materials to contact lens makers.

The lens makers do most of the R&D for new functional monomers and polymers, Smith explains, because their goal is to develop innovations and protect them with patents. The job of firms such as Monomer-Polymer is to synthesize the new molecules. “In the supply chain, we are really focused on the molecule requirement, specifications, and purity of what is required for that material,” he says.

Suppliers such as Monomer-Polymer provide custom versions of workhorse monomers such as Tris methacrylate and other siloxanes, which are hydrophobic, and HEMA and N-vinylpyrrolidone, both hydrophilic.

Different brands of lenses—even from the same company—can contain totally different combinations of monomers that firms such as Smith’s supply exclusively. “Companies don’t want to work with us on a specialized material just to have us sell it to a competitor; that would be a quick way to go out of business,” Smith comments.

The materials are designed in accordance with the specific manufacturing processes of each company. And behind the scenes, firms have invested billions of dollars in manufacturing, the University of Alabama’s Nichols says. Last year, for example, CooperVision spent more than half of its profits on capital investments.

Diamanti says the investment means the company has the infrastructure to make lenses for a wide variety of customers. Some may need stronger prescriptions with higher refractive indexes or special weighted—called toric—lenses to correct astigmatism. And older customers need a range of multifocal options.

“It was a business decision because everyone should have a contact lens made for them,” Diamanti says. “We don’t want to say, ‘Sorry, you have to wear glasses.’ ”

Putting manufacturing and material innovations together has also made daily disposable lenses, which eliminate the need for solutions and cleaners, accessible to more consumers. As a bonus, using a fresh lens every day keeps away bacteria and deposits that can lead to eye health problems.

But making several hundred more lenses per customer requires lower-cost manufacturing processes. Most soft lenses are made in double-sided plastic optical molds that give the two surfaces different shapes. The molds are filled with a mixture of monomers and polymers and cured by free-radical polymerization.

In tandem with the shift to more daily lens use, Alcon developed a new method called Lightstream. Clear glass and quartz molds hold the monomer-polymer mixture. The molds are exposed to ultraviolet light through a shadow-masking pattern that precisely forms the edges of the lens in the liquid mixture. In that process, the surface of the lens never touches the mold itself.

The need for big investments in materials, marketing, and manufacturing makes the industry a tough one for start-ups, points out Karen Havenstrite, CEO of Tangible Science. Her company developed a coating material based on polyethylene glycol that it says can make lenses comfortable for patients with severe dry eye. “You can apply it across almost all material—rigid lenses, soft hydrogels, or silicone hydrogels. It’s a layer of material that is a lot like your natural cornea.”

Tangible Science found its route to market through custom lens companies that work with eye care professionals to serve people with special requirements. “That is the market with the most innovation need and not as much competition,” Havenstrite observes. Custom firms make lenses the old-fashioned way: one at a time on a lathe. The small scale allowed Tangible Science to optimize its process and get customer feedback.

Putting the coating on mass-made soft lenses, which Havenstrite hopes to do by early next year, means Tangible Science must adapt its chemistry to work on manufacturing lines that produce billions of lenses.

“Figuring out how to do that easily is a challenge,” she says.

New roles for contact lenses
 

Today’s contact lenses do only one thing: bend light. They help an incorrectly shaped cornea—the eye’s natural lens—focus light rays right on the surface of the retina. But future lenses could be designed to arrest the progress of vision problems or interact with the body in new ways using electronics.

The alarming growth in myopia has made the condition a popular subject for researchers. Patients with myopia have elongated corneas that focus light in front of the retina. Myopia generally appears in childhood and can advance at different rates, normally stabilizing around age 18 or 20, says Donald Mutti, an optometrist and researcher at Ohio State University.

It’s well known that myopia can be genetically inherited. In addition, kids who aren’t exposed to bright outdoor light are more likely to develop it. But time outdoors, Mutti says, has not been shown to slow progression once myopia develops. He is working on a three-year clinical trial to find out whether a special kind of contact lens can slow or stop the progression of myopia in children as young as seven.

The lenses were first designed to help patients with presbyopia—the loss of ability as we age to adjust focus between near and far objects. That’s why older people often need reading glasses. Multifocal contact lenses, like bifocal glasses, add an area of magnification to help see close up.

But in younger patients, studies have shown, the contact lenses can slow the elongation of the eye. In children, the magnifying portion of the lens “gives the eye a growth control signal that the wearer isn’t even aware of,” Mutti says.

Enhancing contact lenses with electronics is another, more futuristic, way to add functionality. For example, such souped-up lenses could offer real-time focusing help for people with more severe presbyopia, CooperVision’s Diamanti says. Other possibilities include lenses that monitor sleep, glucose levels, or other biomarkers. They could dispense medications or even display images.

These efforts are benefiting from innovations in electronics, including miniaturization and transparent conducting materials. But the challenges are immense. In 2014, Novartis made a splash when it announced it would license so-called smart lens technology from Google. Early this month, Novartis Chair Joerg Reinhardt told shareholders that smart lenses are a high-risk project that will require breakthroughs in new materials.

A search of journal articles and patents by CAS, a division of the American Chemical Society, shows that scientists are testing materials such as organic light-emitting diodes, conducting polymers, and graphene for use in contact lenses. Companies including Google, IBM, LG Chem, Johnson & Johnson, and Samsung have disclosed potential plans for sensors, circuits, power supplies, liquid-crystal displays, and signaling capabilities.

“You can reasonably assume that any function your TV or smartphone has now could be implemented on a contact lens,” says Drew Evans, a professor in the thin films coatings group at the University of South Australia. His team is looking for conductive materials that are compatible with contact lenses and can be incorporated into lens manufacturing.

Evans worked with an international team to put hydrophilic organic electrodes on the surface of contact-lens-style hydrogels. They showed that vapor-phase deposition could be used to coat lenses with a biocompatible, conductive polymer called poly(3,4-ethylenedioxythiophene) (ACS Appl. Mater. Interfaces 2016, DOI: 10.1021/acsami.5b10831).

Such research advances are being tracked closely at CooperVision, Diamanti says. But scaling new technology for mass production is a grand challenge, he cautions. The company is hoping for functional electronics that can be applied using its current manufacturing methods. Otherwise he’s concerned that the benefits will be out of the reach of most customers.

“What are you willing to pay for a contact lens?” he asks.